Infrared (IR)-to-visible light up-conversion devices have attracted a great deal of research interest due to the potential application in night vision, range finding, security, and semiconductor wafer inspections. Early near infrared (NIR) up-conversion devices were mostly based on the heterojunction structure of inorganic semiconductors. These devices consist of two parts in series: one part for photodetection and another for luminescence. The up-conversion devices are mainly distinguished by the method of photodetection. Up-conversion efficiencies of these devices are generally low. For example, one NIR-to-visible light up-conversion device that integrates a light-emitting diode (LED) with a semiconductor based photodetector exhibits a maximum external conversion efficiency of 0.3%. A hybrid organic/inorganic up-conversion device, having an inorganic InGaAs/InP photodetector integrated with an organic light-emitting diode (OLED), exhibits an external conversion efficiency of only 0.25%. Such inorganic and hybrid up-conversion devices are expensive to fabricate and processes and their fabrication is not compatible with large area applications.
Ni et al., Jpn. J. Appl. Phys. 2001, 40, L948 and Chikamatsu et al. Appl. Phys. Lett. 2002, 81, 769 disclose all organic up-conversion devices by coupling fluorescent OLEDs with a titanyl phthalocyanine (TiOPc) photosensitive hole injection layer to exhibited NIR-to-blue and red-to-green up-conversion, respectively. These all organic up-conversion devices display very low conversion efficiencies (less than 0.05%). The photodetectors used in the up-conversion devices have low quantum efficiencies, as the organic sensitizer yield photogenerated excitons having low charge-dissociation efficiency and the fluorescent OLEDs exhibit external quantum efficiencies (EQEs) of less than 5%, resulting in the low overall up-conversion efficiencies.